Without knowing what weight of kettlebells you are using it is difficult to respond intelligently. Using challenging weight kettlebell (s) you should get a through workout in that time period. Since the research ranks strength training ahead of cardio in effectiveness I have my clients do strength workouts three times a week but with a class you are restricted to when it is scheduled.
If you go to www.dragondoor.com
you can research kettlebell training and the recommended weights for women to use.